This invention relates to a process for preparing unsaturated alcohols and more particularly to a process for the preparation of terminally unsaturated alcohols from diols.
Unsaturated aliphatic alcohols are well-known commodities, having varied utilities, and are prepared by a variety of techniques.
For example, U.S. Pat. No. 2,086,713 to Grun describes a process of producing olefin alcohols by mixing dihydroxy alcohols in the liquid phase with a catalyst selected from the group consisting of hydroxides of aluminum, zirconium, titanium and thorium and heating the mixture to temperature above the boiling point of water.
U.S. Pat. No. 3,862,964 to Weisang et al. discloses a catalyst for dehydrating diols which consists of one mixed or unmixed pyrophosphate of at least one metal chosen from the group consisting of lithium, sodium, strontium and barium, and a compound of chromium chosen from the group consisting of chromium oxide and chromium phosphate in an amount less than about 2% of the total weight of the catalyst. To the same effect is U.S. Pat. No. 3,957,900, also of Weisang et al., which describes a specific method of dehydration including contacting the diol in the vapor phase in the presence of inert gas with a mechanically strengthened catalyst formed by calcining a mass formed by mixing finely divided solid particles of at least one pyrophosphate and one acid orthophosphate of a metal belonging to the group consisting of lithium, sodium, strontium and barium.
U.S. Pat. No. 3,670,032 to Romanelli describes the preparation of unsaturated alcohols and ethers through the reaction of C.sub.4 to C.sub.6 aliphatic conjugated diolefins with water, a lower alkanol in the presence of a zero valent palladium based catalyst system, e.g., triphenylphosphine palladium, and a basic cocatalyst selected from the group consisting of tetraalkyl and trialkylaralkyl ammonium hydroxide and alkoxides having 4 to 20 carbon atoms, at a temperature between 0.degree. and 125.degree. C.
U.S. Pat. No. 2,454,936 to Morey discloses a process for preparation of aliphatic unsaturated monohydric alcohols by adding water, not in excess of 10 percent by total weight, to an aliphatic dihydric alcohol having the following structural formula: ##STR1## in which R.sup.1 and R.sup.2 are alkyl radicals, R.sup.3 and R.sup.4 are one of hydrogen and alkyl radicals, and n is an integer from 1 to 4, and adding thereto a dehydration catalyst selected from the group consisting of p-toluenesulfonic acid, iodine, aniline hydroiodide and hydrogen iodide. The mixture is rapidly distilled and condensed yielding an oil condensate containing isomeric monomeric monohydric unsaturated alcohols.
U.S. Pat. No. 2,583,426 to Hillyer, et al. relates to the production of unsaturated primary alcohols containing five or more carbon atoms which comprises contacting an epoxy compound having olefinic unsaturation with a Grignard reagent.
U.S. Pat. No. 3,721,714 to Fenton describes a process for preparing aldehydes and alcohols by contacting a dicarbohydryl carbonate with a catalyst comprised of a complex of a Group VIII noble metal and a biphyllic ligand (e.g. to triphenylphosphine) at a temperature between 150.degree. C. and 250.degree. C. Similarly, U.S. Pat. No. 3,784,616 to Fenton shows a process for the preparation of aldehydes and alcohols by contacting dihydrocarbyl oxalate with a catalyst comprising a Group VIII noble metal and biphyllic ligand at a temperature between 150.degree. C. and 250.degree. C. and at a pressure sufficient to maintain liquid phase reaction.
J. W. Hill and W. H. Carothers, J. Am. Chem. Soc., 55, 5031(1933) disclose a process for the preparation of cyclic ester products by depolymerization of polyesters. It is also disclosed therein, that 9-decen-1-ol is a by-product from the sodium methoxide catalyzed depolymerization of polymeric decamethylene carbonate. The yield of 9-decen-1-ol is only about 2 percent wherein the principal products of the reaction are the cyclic carbonate and cyclic dicarbonate.
Moreover, Searles et al., J. Am. Chem. Soc., 82, 2928(1960), disclose a process for the formation of terminally unsaturated alcohols by the pyrolysis of cyclic carbonates in the presence of a basic catalyst such as potassium cyanide (KCN), while Williams et al. J.O.C. 23, 676 (1958) disclose the formation of terminally unsaturated alcohols from carbonates in the absence of a catalyst. These processes are not totally satisfactory because of the low yields obtained and, in the case of Williams et al., the high temperatures (500.degree. C.) required to achieve pyrolysis.
Thus, while the art is cognizant of many procedures for the preparation of unsaturated alcohols, other simpler, less cumbersome, more economic processes producing high yields of valuable product are very desirable.